If that field is not blank, then click the little box icon to the right of the text field, and copy/paste the URL https://github.com/chipKIT32/chipKIT-core/raw/master/package_chipkit_index.json onto the next line of the text entry field. Arduino lets you have as many different cores as you want loaded into the IDE as long as each URL is on a separate line. Click OK to close the Additional Boards Manager URLs dialog box and then click OK again to close the Preferences dialog box.

Now select the Tools->Board->Board Manager menu from the Arduino IDE, and it will open up the Boards Manager window. From there, scroll down until you see the chipKIT board. Click once on any of the text in the chipKIT section, and you will see a button appear that says "Install". It will take some time to download all of the chipKIT components and install them, but when it's done, you can click the Close button to close the Board Manager window.

After completing these steps Visual Studio will show the same chipKIT boards for development as the Arduino Ide. If you installed chipKIT using the Arduino Ide tools while Visual Studio was already open then click "Tools>Visual Micro>Reload Toolchains" or Restart the Ide.

Note that as new versions of the chipKIT-core files are released, you will get to update your chipKIT-core files from inside the Arduino IDE, and select which version you'd like to install/update to.

Drivers

Most chipKIT boards use FTDI drivers, and your computer probably has those on it already. Some chipKIT boards (like the Fubarinos, chipKIT-PI, and DP32) use the PIC32's built-in USB peripheral to communicate with the PC, and they need a driver file when used on a Windows PC. The following link is for Windows PCs, and contains the FTDI drivers and the chipKIT USB drivers. If you plug your chipKIT board into your computer and it can't find the right drivers, then download and unzip this, and point Windows to the unzipped contents to install the right driver: